1. Field of the Invention
This invention is directed to an apparatus, to a method of manufacture and to an article of manufacture. More specifically, this invention is directed to a semi-automated apparatus and method for the manufacture of softgoods (e.g. footwear) involving injection molding of one or more components thereof. The softgoods resulting from such process are of a consistently high quality and appearance; and, the union or bond between the injection molded component and the non-injection molded component is both aesthetically attractive and forms an essentially permanent and complete seal therebetween.
2. Description of the Prior Art
In the manufacture of softgoods, such as footwear having injection molded soles, the process generally involves pre-forming a footwear upper from leather, canvas or a synthetic material; placement of the upper onto a foot form (also "last") of the appropriate size; securing the upper on the last by a drawstring-like cord which "ties" the sole face of an unfinished upper firmly to the last; placement of the last and upper in operative relation to the sole mold so as to extend at least a portion of the upper into the sole mold cavity; closing the mold so as to clamp the mold onto the last and the upper; and, injection of a plastic resin into the sole mold cavity. Upon setting of the resin, the mold is separated and, thereafter, the finished footwear removed from the last. The foregoing process is preferably performed on a carousel-like apparatus wherein each of the sequential operations in the manufacture is timed to the injection molding cycle and a completed manufacturing cycle takes at least one, and preferably two, complete revolutions of the carousel to allow adequate time for the setting of the resin in the mold before opening of the mold and the removal of the finished footwear from the last. In order to accommodate the continuous manufacture of footwear on this style of equipment, each of the workstations is provided with support that can accommodate two lasts, and such support pivots in respect to the rotating platform so as to position a last at a given workstation relative to a workman. The rotation of the last support, thus, provides for the continuous operation of the equipment while permitting additional time for the sole of the completed footwear to set in the mold cavity before the removal thereof.
As is appreciated by the prior art, the foregoing process is generally modified or adjusted to accommodate the different materials used in the manufacture of such footwear, specifically, to insure the complete and essentially uniform bonding of the upper and the injection molded sole. Where for example, the sole is injection molded from PVC (polyvinyl chloride or an analog thereof) the bonding of the sole and the upper is accomplished without any special processing or accessory materials (bonding agents, adhesives, etc.). More specifically, the bonding of the PVC sole to the upper is apparently independent of material choice for the upper, and essentially complete and uniform bonding therebetween is effected where the upper is fabricated from a natural material, such as leather, or a synthetic material, such as vinyl. Injection molded PVC soles are acceptable for the less expensive types of footwear, however, thermosetting plastic rubber compounds (also herein referred to a "TPR") are preferable materials for injection molded soles as providing more comfort and a more attractive finished product. Unfortunately, the characteristic bonding properties of TPR compounds and the footwear upper require that an additional bonding agent be applied to the upper prior to injection molding of the sole to insure complete and essentially uniform adhesion of the upper to the sole in the finished goods. In the intermediate step of applying the bonding agent to the upper prior to placement of the sole mold in operative relation to the upper and the last, a mask must be used to insure that excess bonding agent is not misapplied to the upper so as to visibly detract from the appearance of the footwear upon the completion of the injection molding of the sole. Typically, this mask is sized appropriately to the operation for which it is intended and generally hand-held in place while the bonding agent applied with a brush or spray applicator to the upper. Because this intermediate step in the manufacturing process is generally performed manually and thus otherwise imprecise, it is subject to operator error and produces a significant number of blemished footwear that either require "dressing" of the blemish or, if irremediable, discarding the blemished item.
In an effort to add precision to this process and thereby minimize the occurrence of misapplication of bonding agent, or the application of excess binding agent, a variety of make-shift devices have been tried and rejected. More specifically, past efforts at automating the placement of a mask in relation to the upper have generally been inadequate as providing an ineffective seal between the upper and the mask, thus, allowing excess bonding agent to continue to cause blemishes in the finished footwear; and, alternatively, where effective sealing has been attempted between the mask and the upper, by automation of the masking process, such process has all to often resulted in increased risk of injury to the individuals operating such equipment because of inadvertent place mere of a hand or finger in the powered masking device, thereby causing serious injury. Accordingly, there has and continues to be a need to provide improved equipment and techniques for automating the manufacture of footwear, specifically footwear produced with injection molded soles formed from thermosetting plastic rubber compounds.